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From: Geliang Tang <geliang@kernel.org>
To: mptcp@lists.linux.dev
Cc: Geliang Tang <tanggeliang@kylinos.cn>
Subject: [PATCH mptcp-next v6 2/5] mptcp: pm: add accept_new_subflow()
interface
Date: Fri, 28 Mar 2025 12:01:32 +0800
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<2c5a2dc15229df637c5523fd63b2b5dd88619615.1743133948.git.tanggeliang@kylinos.cn>
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From: Geliang Tang <tanggeliang@kylinos.cn>
The helper mptcp_pm_is_userspace() is used to distinguish userspace PM
operations from in-kernel PM in mptcp_can_accept_new_subflow(). It seems
reasonable to add a mandatory .accept_new_subflow interface for struct
mptcp_pm_ops.
The boolean type 'allow' parameter is used to control whether to allow new
subflow unconditionally.
A new helper mptcp_pm_accept_new_subflow() is added in pm.c to ensure that
pm->ops is only used in pm.c.
This interface of the in-kernel PM is implemented as a wrapper of
READ_ONCE(pm->accept_subflow), and this interface of the userspace PM is
implemented as a wrapper of mptcp_userspace_pm_active().
To reduce the dependency on mptcp_pm_is_userspace() to identify userspace
PM from in-kernel PM by using mptcp_pm_accept_new_subflow() helper in
mptcp_pm_allow_new_subflow().
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
---
include/net/mptcp.h | 1 +
net/mptcp/pm.c | 38 +++++++++++++-------------------------
net/mptcp/pm_kernel.c | 16 ++++++++++++++++
net/mptcp/pm_userspace.c | 7 +++++++
net/mptcp/protocol.h | 25 +++++++++++++++++++++++++
net/mptcp/subflow.c | 6 ++----
6 files changed, 64 insertions(+), 29 deletions(-)
diff --git a/include/net/mptcp.h b/include/net/mptcp.h
index 4cf59e83c1c5..549b8075cc86 100644
--- a/include/net/mptcp.h
+++ b/include/net/mptcp.h
@@ -123,6 +123,7 @@ struct mptcp_pm_ops {
struct mptcp_pm_addr_entry *skc);
bool (*get_priority)(struct mptcp_sock *msk,
struct mptcp_addr_info *skc);
+ bool (*accept_new_subflow)(struct mptcp_sock *msk, bool allow);
=20
char name[MPTCP_PM_NAME_MAX];
struct module *owner;
diff --git a/net/mptcp/pm.c b/net/mptcp/pm.c
index 4ed6a2ccb112..a96f3495d220 100644
--- a/net/mptcp/pm.c
+++ b/net/mptcp/pm.c
@@ -460,38 +460,25 @@ void mptcp_pm_new_connection(struct mptcp_sock *msk, =
const struct sock *ssk, int
mptcp_event(MPTCP_EVENT_CREATED, msk, ssk, GFP_ATOMIC);
}
=20
+bool mptcp_pm_accept_new_subflow(struct mptcp_sock *msk, bool allow)
+{
+ return msk->pm.ops->accept_new_subflow(msk, allow);
+}
+
bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk)
{
struct mptcp_pm_data *pm =3D &msk->pm;
- unsigned int subflows_max;
int ret =3D 0;
=20
- if (mptcp_pm_is_userspace(msk)) {
- if (mptcp_userspace_pm_active(msk)) {
- spin_lock_bh(&pm->lock);
- pm->subflows++;
- spin_unlock_bh(&pm->lock);
- return true;
- }
- return false;
- }
-
- subflows_max =3D mptcp_pm_get_subflows_max(msk);
-
- pr_debug("msk=3D%p subflows=3D%d max=3D%d allow=3D%d\n", msk, pm->subflow=
s,
- subflows_max, READ_ONCE(pm->accept_subflow));
-
- /* try to avoid acquiring the lock below */
- if (!READ_ONCE(pm->accept_subflow))
+ if (!mptcp_pm_accept_new_subflow(msk, true))
return false;
=20
- spin_lock_bh(&pm->lock);
- if (READ_ONCE(pm->accept_subflow)) {
- ret =3D pm->subflows < subflows_max;
- if (ret && ++pm->subflows =3D=3D subflows_max)
- WRITE_ONCE(pm->accept_subflow, false);
+ ret =3D mptcp_pm_accept_new_subflow(msk, false);
+ if (ret) {
+ spin_lock_bh(&pm->lock);
+ pm->subflows++;
+ spin_unlock_bh(&pm->lock);
}
- spin_unlock_bh(&pm->lock);
=20
return ret;
}
@@ -1060,7 +1047,8 @@ struct mptcp_pm_ops *mptcp_pm_find(const char *name)
=20
int mptcp_pm_validate(struct mptcp_pm_ops *pm_ops)
{
- if (!pm_ops->get_local_id || !pm_ops->get_priority) {
+ if (!pm_ops->get_local_id || !pm_ops->get_priority ||
+ !pm_ops->accept_new_subflow) {
pr_err("%s does not implement required ops\n", pm_ops->name);
return -EINVAL;
}
diff --git a/net/mptcp/pm_kernel.c b/net/mptcp/pm_kernel.c
index 8935df61aa50..eaf73c4cedd3 100644
--- a/net/mptcp/pm_kernel.c
+++ b/net/mptcp/pm_kernel.c
@@ -1399,6 +1399,21 @@ static struct pernet_operations mptcp_pm_pernet_ops =
=3D {
.size =3D sizeof(struct pm_nl_pernet),
};
=20
+static bool mptcp_pm_kernel_accept_new_subflow(struct mptcp_sock *msk,
+ bool allow)
+{
+ bool ret =3D false;
+
+ if (READ_ONCE(msk->pm.accept_subflow)) {
+ if (allow)
+ return true;
+
+ ret =3D mptcp_pm_accept_subflow(msk);
+ }
+
+ return ret;
+}
+
static void mptcp_pm_kernel_init(struct mptcp_sock *msk)
{
bool subflows_allowed =3D !!mptcp_pm_get_subflows_max(msk);
@@ -1422,6 +1437,7 @@ static void mptcp_pm_kernel_init(struct mptcp_sock *m=
sk)
struct mptcp_pm_ops mptcp_pm_kernel =3D {
.get_local_id =3D mptcp_pm_kernel_get_local_id,
.get_priority =3D mptcp_pm_kernel_get_priority,
+ .accept_new_subflow =3D mptcp_pm_kernel_accept_new_subflow,
.init =3D mptcp_pm_kernel_init,
.name =3D "kernel",
.owner =3D THIS_MODULE,
diff --git a/net/mptcp/pm_userspace.c b/net/mptcp/pm_userspace.c
index d9b0a93e42f6..31da3b9f4cc8 100644
--- a/net/mptcp/pm_userspace.c
+++ b/net/mptcp/pm_userspace.c
@@ -683,6 +683,12 @@ int mptcp_userspace_pm_get_addr(u8 id, struct mptcp_pm=
_addr_entry *addr,
return ret;
}
=20
+static bool mptcp_pm_userspace_accept_new_subflow(struct mptcp_sock *msk,
+ bool allow)
+{
+ return mptcp_userspace_pm_active(msk);
+}
+
static void mptcp_pm_userspace_release(struct mptcp_sock *msk)
{
mptcp_userspace_pm_free_local_addr_list(msk);
@@ -691,6 +697,7 @@ static void mptcp_pm_userspace_release(struct mptcp_soc=
k *msk)
static struct mptcp_pm_ops mptcp_pm_userspace =3D {
.get_local_id =3D mptcp_pm_userspace_get_local_id,
.get_priority =3D mptcp_pm_userspace_get_priority,
+ .accept_new_subflow =3D mptcp_pm_userspace_accept_new_subflow,
.release =3D mptcp_pm_userspace_release,
.name =3D "userspace",
.owner =3D THIS_MODULE,
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 3d51898a2781..134b46b53014 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -1008,6 +1008,7 @@ bool mptcp_pm_addr_families_match(const struct sock *=
sk,
void mptcp_pm_subflow_chk_stale(const struct mptcp_sock *msk, struct sock =
*ssk);
void mptcp_pm_new_connection(struct mptcp_sock *msk, const struct sock *ss=
k, int server_side);
void mptcp_pm_fully_established(struct mptcp_sock *msk, const struct sock =
*ssk);
+bool mptcp_pm_accept_new_subflow(struct mptcp_sock *msk, bool allow);
bool mptcp_pm_allow_new_subflow(struct mptcp_sock *msk);
void mptcp_pm_connection_closed(struct mptcp_sock *msk);
void mptcp_pm_subflow_established(struct mptcp_sock *msk);
@@ -1184,6 +1185,30 @@ static inline void mptcp_pm_close_subflow(struct mpt=
cp_sock *msk)
spin_unlock_bh(&msk->pm.lock);
}
=20
+static inline bool __mptcp_pm_accept_subflow(struct mptcp_sock *msk)
+{
+ unsigned int subflows_max =3D mptcp_pm_get_subflows_max(msk);
+ struct mptcp_pm_data *pm =3D &msk->pm;
+ bool ret;
+
+ ret =3D pm->subflows < subflows_max;
+ if (ret && pm->subflows + 1 =3D=3D subflows_max)
+ WRITE_ONCE(pm->accept_subflow, false);
+
+ return ret;
+}
+
+static inline bool mptcp_pm_accept_subflow(struct mptcp_sock *msk)
+{
+ bool ret;
+
+ spin_lock_bh(&msk->pm.lock);
+ ret =3D __mptcp_pm_accept_subflow(msk);
+ spin_unlock_bh(&msk->pm.lock);
+
+ return ret;
+}
+
void mptcp_sockopt_sync_locked(struct mptcp_sock *msk, struct sock *ssk);
=20
static inline struct mptcp_ext *mptcp_get_ext(const struct sk_buff *skb)
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index 409bd415ef1d..b13a679bdf05 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -58,12 +58,10 @@ static void subflow_generate_hmac(u64 key1, u64 key2, u=
32 nonce1, u32 nonce2,
mptcp_crypto_hmac_sha(key1, key2, msg, 8, hmac);
}
=20
-static bool mptcp_can_accept_new_subflow(const struct mptcp_sock *msk)
+static bool mptcp_can_accept_new_subflow(struct mptcp_sock *msk)
{
return mptcp_is_fully_established((void *)msk) &&
- ((mptcp_pm_is_userspace(msk) &&
- mptcp_userspace_pm_active(msk)) ||
- READ_ONCE(msk->pm.accept_subflow));
+ mptcp_pm_accept_new_subflow(msk, true);
}
=20
/* validate received token and create truncated hmac and nonce for SYN-ACK=
*/
--=20
2.43.0